Desirable and Undesirable Characteristics of Offshore Yachts

[MikeJohns]

No, actually - its all pretty much what we have already agreed.

As a general statement, we all agree that more RM and higher AVS is beneficial, all else being equal. I have stated this repeatedly. we all agree on this.  However, very rarely is all else equal.  You end up with design compromises and trade-offs and where the optimum point for those trade-offs will depend on the specific vessel/owners mission/purposes.

No, they are considering different things, and when you properly read/understand them, they both can/are true.  In theory and in generality, we agree more RM and AVS are beneficial.  BUT when faced with the power of actual 60 breaking waves, in practice the force of the waves can simply wash out the comparatively little differences between the RM/AVS's.  Both of these things are true, both of these things were also findings from the post fastnet studies.

Sorry I'm running a bit behind.

If you take out the knockdowns and just look at capsizes it’s a different picture. There were exactly the same trends in the 1998 S-H between stability and capsize as previously observed by Wolfston.  Their guide reasonably accurately indicates risk just from LPS for a raft of different monohulls. Barry Deakin is the person to talk to about this.

Kim Taylor ( NA who lambasted the clubs whitewash) pointed out that even in the absence of full stability data If you simply multiply the DL ratio by LPS and plot that against length you get an even better indication of vulnerability. It points to a poor showing within the IMS fleet in the S-H casualties.

As for the Fastnet that lead to Marchaj's tome. I thought the club report from the Fastnet was more honest that the CYCA's.  It stated for a start that a lot of the racing fleet actually had no experience in a storm !

Seamanship can make a less seaworthy boat safe everyone agrees that, but small increases in wave height might not be as small as you think for lighter boats.

AMC ( Renilson 1999) found for a Farr 40 ( IMS racer) to be capsized laying ahull beam on, that with a LPS at 110 degrees it required a 4.4m wave but at 115 degrees it took a 5.4 m fully breaking wave.

That extra meter is quite significant for a 5 degree increase in LPS.

 

[Panoramix]

f you take out the knockdowns and just look at capsizes it’s a different picture. There were exactly the same trends in the 1998 S-H between stability and capsize as previously observed by Wolfston.  

If you cherry pick evidence that suits you, you can reach any pre-determined conclusion...

 

[Bob Perry]

Zonker:

No. Wil was an intern with me when he was 15. He's 24 years old now and he did that 3D model about 2 years ago. He is now working with me on a new design, a 2021 answer to the Islander 28. They built 600 28's and I'm trying to capture the elements that made the I-28 so successful in a more modern hull and rig configuration. I'll post drawings soon. It's getting close to the time when I need to pass the baton.

 

[Jud - s/v Sputnik]

I asked Beth about Curlew - she remembers these details better. She spent more time with 'the English crowd' than I did. We wintered 2 winters in Ireland and she did speaking trips to London , used our reciprocal privilege's at the Royal Themes which was rather a nice perk, while I stayed and worked on the boat): "new cold molded outer skin of kauri with epoxy" she says.  We missed them by just a year (or perhaps two) I think in S Georgia - would have been nice to have met them 'in the wild' so to speak.

Uncomfortable, yea, and if I remember correctly they were wearing 'authentic clothing'.  The Nav they got fuckup a bit (no real criticism - easy to fuck up in a situation like that) and the support vessel had to come over and quietly tell them to change course or they would miss the island.  The team's mountain skills were more solid than the sea skills.

Ta

“Antarctic Oasis” - fantastic and beautiful book.  Some great pics (and history) of Curlew in there.  One of my favourite books.  (I believe they talk in some detail about the Kauri sheathing.) 

 

[estarzinger]

“Antarctic Oasis” - fantastic and beautiful book.  Some great pics (and history) of Curlew in there.  One of my favourite books.  (I believe they talk in some detail about the Kauri sheathing.) 

Have you run across Kicki and Thies work (sailing Hiscock's Wanderer III)?  We first met them in Tasmania - saw some folks sailing a small cruising nice looking boat on and off anchor and invited them over for dinner.  Bumped into them many places afterwards, and for a short while they took the Carr's place in S. Georgia as the resident wooden boat helpers.  Also have really great photos, they write very well also but like with Deborah & Rolfe (Northern light) they include quite a strong anti-capitalist's voice in their writing which was not appreciated by American publishers.

But they are/were another small wooden boat doing very special quite difficult stuff.

30' of wooden boat IS REALLY all you need, to go almost anywhere (including wintering in S Georgia).  It is a hard message to get across today with all the selling pressure toward large more complicated vessels.  You do need to be decently tough and competent.

 

[MikeJohns]

If you cherry pick evidence that suits you, you can reach any pre-determined conclusion...

That's actually the point. But in this case it's including data that shouldn't be there. 

It's pretty simple; Knockdown and recovery within LPS are not considered Stability Casualties in Naval Architecture. 

If there is enough reserve stability for the vessel to re-right from a knockdown and not to proceed into a capsize then it's considered to have adequate stability. 

That's what Wolfston institutes extensive  work was all about, coming up with some simple risk assesment based  on the most significant single criteria for modern hullforms that being stability.  Risk being Hazard (significant breaking wave) and Exposure ( likelihood of encounter).  

Researchers have propsed that the best indicator of whether or not a boat is inverted or recovers is the total area under the RM curve from 100 to 130 degrees.  That appears to be a better screening factor but it's too hard to apply to standards in practice.

 

[olaf hart]

Have you run across Kicki and Thies work (sailing Hiscock's Wanderer III)?  We first met them in Tasmania - saw some folks sailing a small cruising nice looking boat on and off anchor and invited them over for dinner.  Bumped into them many places afterwards, and for a short while they took the Carr's place in S. Georgia as the resident wooden boat helpers.  Also have really great photos, they write very well also but like with Deborah & Rolfe (Northern light) they include quite a strong anti-capitalist's voice in their writing which was not appreciated by American publishers.

But they are/were another small wooden boat doing very special quite difficult stuff.

30' of wooden boat IS REALLY all you need, to go almost anywhere (including wintering in S Georgia).  It is a hard message to get across today with all the selling pressure toward large more complicated vessels.  You do need to be decently tough and competent.

Kiki and Thies spent quite a while around Barnes Bay, we’re you there at the same time as well?

 

[estarzinger]

Kiki and Thies spent quite a while around Barnes Bay, we’re you there at the same time as well?

yea, that is exactly where we first met them. The boat looked so lovely under sail.  We were passing thru reasonably quickly heading east bound - Steward island and back to Chile.

Jud - Port Pegasus on Steward island - I sought out exactly where Parlier repaired his mast.  We hung out there for a bit just to soak up the atmosphere.

 

[Panoramix]

That's actually the point. But in this case it's including data that shouldn't be there. 

It's pretty simple; Knockdown and recovery within LPS are not considered Stability Casualties in Naval Architecture. 

If there is enough reserve stability for the vessel to re-right from a knockdown and not to proceed into a capsize then it's considered to have adequate stability. 

That's what Wolfston institutes extensive  work was all about, coming up with some simple risk assesment based  on the most significant single criteria for modern hullforms that being stability.  Risk being Hazard (significant breaking wave) and Exposure ( likelihood of encounter).  

Researchers have propsed that the best indicator of whether or not a boat is inverted or recovers is the total area under the RM curve from 100 to 130 degrees.  That appears to be a better screening factor but it's too hard to apply to standards in practice.

Here is the diagram you posted before :

View attachment 442512

I am not sure where this idea of knockdown vs capsize comes from...

Seriously looking at this graph, range of stability doesn't seem to be such a big factor, as all kind of boats seem to have been rolled!!! Actually you would need to plot on the graph boats that haven't been rolled to reach a meaningful conclusion.

 

[Jud - s/v Sputnik]

Have you run across Kicki and Thies work (sailing Hiscock's Wanderer III)?  We first met them in Tasmania - saw some folks sailing a small cruising nice looking boat on and off anchor and invited them over for dinner.  Bumped into them many places afterwards, and for a short while they took the Carr's place in S. Georgia as the resident wooden boat helpers.  Also have really great photos, they write very well also but like with Deborah & Rolfe (Northern light) they include quite a strong anti-capitalist's voice in their writing which was not appreciated by American publishers.

But they are/were another small wooden boat doing very special quite difficult stuff.

30' of wooden boat IS REALLY all you need, to go almost anywhere (including wintering in S Georgia).  It is a hard message to get across today with all the selling pressure toward large more complicated vessels.  You do need to be decently tough and competent.

I used to walk to the former bookstore in the former WTC (from my old office at Moody’s on Church St. in lower Manhattan) to escape the corporate office madness, and came across “Antarctic Oasis” there.  I bought it immediately then- it helped light a fire in my mind (along with “North to the Night”, which my father gave me).  I was like, ‘oh, so there really are much more interesting ways to live than this madness’  

30 feet of wooden boat is all you need, as you say - but did you know Curlew has no lifelines?  Of course, they’re probably of somewhat dubious value (at least their name is of dubious value, since it implies to a newbie that having them will “save your life”?!), but it’s incredible they sailed all that way, even to Antarctica with hank-on sails and no lifelines on the foredeck...

I have indeed read about Kiki and Thies.  Hadn’t realized they did any writing beyond magazines...with an anti-capitalist slant: even better . I’m sure they have a very different perspective on the world from many people...

 

[Jud - s/v Sputnik]

Jud - Port Pegasus on Steward island - I sought out exactly where Parlier repaired his mast.  We hung out there for a bit just to soak up the atmosphere.

Must get down there...one of the coolest bits of modern seamanship ever.  Like being on Pitcairn Isl. Must get south of Canada first . (Currently sorting boom, awaiting new mainsail, planning solar panels.  I’m sure I left out something else required to give the boat more desirable characteristics as an offshore yacht  )

 

[estarzinger]

.  I’m sure I left out something else required to give the boat more desirable characteristics as an offshore yacht  )

the perfect coffee maker, or two or three 

 

[Jud - s/v Sputnik]

the perfect coffee maker, or two or three 

I finally nixed the pressurized stove-too espresso maker - you know the ones I mean?  It was a hardship making coffee for the two of us, Leah and I - since it was too small to make enough coffee for two people - so you’d have  to set it up and make another one after making the first one.  Ugh!  Made good coffee, but I like to minimize “cooking”, and it would require two times at the stove.  Have a French press now...good until the carafe breaks...(or has this been covered in depth in another thread?  )

 

[MikeJohns]

Here is the diagram you posted before :

I am not sure where this idea of knockdown vs capsize comes from...

Seriously looking at this graph, range of stability doesn't seem to be such a big factor, as all kind of boats seem to have been rolled!!! Actually you would need to plot on the graph boats that haven't been rolled to reach a meaningful conclusion.

As a rule a full inversion usually incapacitates the vessel. It's unable to continue and needs to either effect self rescue or be rescued.

A knockdown on it's side should not incapacitate a sailboat if it's designed to go to sea.

Post Fastnet it turned out to be confusing since people used knockdown for capsize as well. The terms B1 and B2 knockdown were introduced to distinguish between a  loss of reserve stability and a  knockdown where the boat is just rolled to it's side and recovers usually with no damage or downflooding if the hatches are closed. 

Now we are back to knockdown and inversion or capsize. Terminology also varies by nation.

I just dragged in some of Wolfstons early casualty analysis, including sailing coastal barges as well as offshore yachts that was pre 1998. This is the sort of casualty analysis you want to see presumably . There were also several other sources of data fro other countries used ( not shown).

The development of the code tied in with the ongoing research into sailboat stability in waves and causes of capsize by a variety of researchers.  

If the plots look a bit sparse it's because they are scientific papers, the only plots are the boats where full stability data was available and verified.

Going back to the S-H boats only one would have been allowed offshore under the MCA code. They added the S-H data later and haven't adjusted the line upward. It varies a bit from the STIX approach.

I just find it very interesting and quite a good rough guide.  But as I said the best indication of capsize resistance according to Barry Deakin is the RM curve from 100 to 130 degrees.

 

[Panoramix]

@MikeJohns, at the very least we need a title and a legend to understand a graph!

 

[CapDave]

Have a French press now...good until the carafe breaks

 

[IStream]

View attachment 443373

I have this exact unit and it's great. 

 

[MikeJohns]

@MikeJohns, at the very least we need a title and a legend to understand a graph!

Sorry I thought it was self explanatory.

It’s simply: “Minimum range of stability required by code of practice. Showing casualties with fleet data. (Casualties symbols solid.)”

Fleet data is taken from events with good representative larger fleets and they plot capsizes against LPS.  

This is nothing radical about this type of analysis it’s bog standard Naval Architecture.

There’s another stability limit code developed this way by Wolfston/MCA for stability limits for sailing craft >24m. Even France uses that !

 

[Cruisin Loser]

Bizarre coincidence territory. An english guy Kevin Carr came to west Texas as a mechanic for Chapparral auto racing in the1980's. He also ref'd Rugby games, I was no. 8 on the local team. Eventually, after I'd started my own company, I hired him to maintain all my company vehicles through a business of his. Great guy.

It wasn't until I bought Sparky that he realized I was a sailor, too. Turned out at some point he'd worked yachts in Bermuda, but he started telling me tales about his younger cousin, Timmy. Hell, he had letters and pics. 

I've never met Tim, but I'd sure like to. One of the only guys alive I'd admit that about, because I'm not much of a fanboy. Real deal, he seems. Kev had a compelling reason Tim did all that remote sailing, but I'll stop there. Like Camp  4 at Yos, there's stories. 

Kev got cancer, bad deal. We took care of him when his insurance puked him up as a nuisance, not an asset, but  a lot of stuff just doesn't have a happy ending. 

 

[Panoramix]

Sorry I thought it was self explanatory.

So what is a square or a triangle for Mr Obvious ?